autoimmune myocarditis (MONDO_0022519) is an autoimmune disease that affects the heart. The condition is characterized by inflammation of the heart muscle (myocardium). Some people with autoimmune myocarditis have no noticeable symptoms of the condition. When present, signs and symptoms may include chest pain, abnormal heartbeat, shortness of breath, fatigue, signs of infection (i.e. fever, headache, sore throat, diarrhea), and leg swelling. The exact underlying cause of the condition is currently unknown; however, autoimmune conditions, in general, occur when the immune system mistakenly attacks healthy tissue. Treatment is based on the signs and symptoms present in each person. In some cases, medications that suppress the immune system may be recommended.